Constellation, Triangle
Triangulum
A simple triangle of stars between Andromeda and Aries, known since ancient Greek times. Some saw in it the Nile delta or the island of Sicily.
From New York on October 13, 2026, the centre of Triangulum rises at 5:19 PM, is highest at 1:36 AM (82° above the horizon in the S) and sets at 9:53 AM.
In the 3D sky
The sky over New York turned towards Triangulum. Drag to look around.
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Evening visibility over the year
Height of the constellation’s centre above the horizon at 10 pm local time on the 15th of each month, from New York. Above about 30° it is well placed.
Name and history
Any three stars make a triangle, so it is not surprising to find one among the constellations. Aratus and Eratosthenes called it Deltoton because it looks like the Greek capital letter delta. Ptolemy listed it as Trigonon, triangle. Aratus described it as having two equal sides and a shorter third. Eratosthenes said it stood for the delta of the river Nile. Hyginus wrote that some people saw it as Sicily, once called Trinacria for its three headlands. In myth Sicily was the home of Ceres, goddess of farming.
Alpha Trianguli is named Mothallah, from the Arabic for ‘the triangle’. In 1687 Johannes Hevelius added a smaller triangle next to it, Triangulum Minus, and called the original Triangulum Majus. The little triangle has since fallen out of use. Its memory survives in the star 6 Trianguli, which the IAU named Triminus in 2025.
Sources: Ian Ridpath, Star Tales: Triangulum, IAU Working Group on Star Names (WGSN): Modern IAU star names
Brightest stars
| Star | Designation | Magnitude | Distance |
|---|---|---|---|
| Alaybasan | β Tri | 3.00 | 127 light-years |
| Mothallah | α Tri | 3.42 | 63 light-years |
| Apdu | γ Tri | 4.03 | 112 light-years |
| Deltoton | δ Tri | 4.84 | 35 light-years |
| Triminus | 6 Tri | 4.94 | 291 light-years |
Facts
| Area | about 133 square degrees (78 of 88) |
|---|---|
| IAU abbreviation | Tri |
| Sky | Northern sky |
| Origin | Listed in Ptolemy’s Almagest, about AD 150, as Trigonon, the triangle |
| Stars brighter than magnitude 5 | 5 |
| Centre (J2000) | 2.2 h, 33° |
Deep-sky objects
Galaxies, clusters and nebulae brighter than magnitude 9, from the OpenNGC catalogue. Most need binoculars or a telescope and a dark sky.
| Object | Type | Magnitude |
|---|---|---|
| M33 · Triangulum Galaxy | Galaxy | 5.8 |
Boundaries: International Astronomical Union, via Astronomy Engine. Areas are computed from the boundaries by sampling (within about one percent). Names and lines: Stellarium. Stars: HYG Database. Deep-sky objects: OpenNGC. Calculated with Astronomy Engine, an open-source library verified against the US Naval Observatory and NASA JPL. Data sources
How to use this page
Choose your place and a night at the top. The answer and the 3D view show where the constellation is, when it is highest and whether it rises at all from where you are. The chart shows its stars and lines, and the tables list its brightest stars and the deep-sky objects inside it.
Frequently asked questions
When is a constellation best seen?
When it is highest in a dark sky, which the page gives for the night you pick. Each constellation is best placed in a particular season, because the stars rise about four minutes earlier every night.
Why can I not see a constellation from my place?
Constellations far south of the celestial equator never rise from northern places, and those far north never rise from southern ones. The page says when this is the case.
What are the constellation boundaries?
The International Astronomical Union divides the sky into 88 areas with official boundaries. The stick figures are only a drawing aid, the boundaries say which constellation a point in the sky belongs to.
Related guides
- How to learn the constellationsStart with one bright pattern you cannot miss, use it as a signpost to its neighbours, and come back a month later: the sky will have turned, and you will know a little more of it.
- Altitude and azimuth: finding things in the skyTwo angles tell you exactly where to look: which direction, and how high.
- Light pollution and dark skies: the Bortle scaleFrom a city centre you can count a few dozen stars. From a truly dark site you can count a few thousand, with the Milky Way bright enough to cast a shadow. The Bortle scale puts a number on the difference.
- Binoculars for stargazing: what to buy and what to look atA pair of 7x50 or 10x50 binoculars shows the craters of the Moon, the moons of Jupiter, dozens of star clusters and the Andromeda Galaxy, for a fraction of the cost of a telescope.